docs: added example of Makefile

Author: matveypashkovskiy

README.md

@@ -1,6 +1,9 @@
-<img src="https://github.com/F-Secure/pytest-rts/raw/master/docs/imgs/pytest-rts-logo.png" width="120px" height="120px"/>
-
-# Coverage-based regression test selection (RTS) plugin for pytest
+<table border="0"><tr>
+ <td width="120px">
+ <img src="https://github.com/F-Secure/pytest-rts/raw/master/docs/imgs/pytest-rts-logo.png"/>
+ </td>
+ <td><h1 style="padding: 0; margin: 0;">Coverage-based regression test selection (RTS) plugin for pytest</h1></td>
+</tr></table>
 
 - [Usage](#usage)
 - [Troubleshooting](#troubleshooting)
@@ -24,6 +27,8 @@ relative_files = True
 3. Execute `pytest --cov=[path to your package] --cov-context=test --cov-config=.coveragerc` which will run the entire test suite and build a mapping database in `.coverage` file
 4. Rename the coverage file `.coverage` produced by `pytest-cov` to your liking. Example: `mv .coverage pytest-rts-coverage`
 
+Note that `--cov-config=.coveragerc` is optional parameter here. For more info see [official docs](https://pytest-cov.readthedocs.io/en/latest/config.html#caveats).
+
 ### Local usage
 
 1. Install `pytest-rts` with `pip install pytest-rts`
@@ -41,6 +46,36 @@ As a result only tests related to changes in working directory and branch will b
 * In pull requests:
  * make sure you have coverage database from the main branch located next to the code
  * run `pytest --rts --rts-coverage-db=[path to database]`
+ 
+One of the ways to organize it in Makefile would be:
+
+```make
+test:
+@[ "$(BRANCH_NAME)" = "master" ] && $(MAKE) test-master || $(MAKE) test-pr
+
+test-master:
+pytest \
+ --exitfirst \
+ --cov \
+ --cov-context=test \
+ --cov-config=.coveragerc
+mv .coverage mapping.db
+git add mapping.db
+git commit -m "test: updated RTS mapping DB"
+git push
+
+test-pr: MASTER_COMMIT=$(shell git merge-base remotes/origin/master HEAD)
+test-pr:
+git checkout $(MASTER_COMMIT) mapping.db
+pytest \
+ --exitfirst \
+ --rts \
+ --rts-coverage-db=mapping.db \
+ --rts-from-commit=$(MASTER_COMMIT) && [ $$? -eq 0 ] || [ $$? -eq 5 ]
+```
+
+Exit code tests/overwrite `&& [ $$? -eq 0 ] || [ $$? -eq 5 ]` is needed in cases when no tests are found for execution.
+See Troubleshooting section for more information.
 
 ## <a name="troubleshooting"></a> Troubleshooting